The present invention generally relates to vehicle weigh-in-motion scales, for example, at-speed scales used in highways (65 mph) and ramp scales (15 mph). But more particularly, the invention applies to the conversion of existing static scales that are designed for weight measurement carried out with the truck at a complete stop.
Because of the increased number of vehicles on the nation highways, considerable effort has been made by the federal and state transportation agencies and motor carriers to increase the efficiency of enforcement operations at the highway weigh-stations. For example, operational tests and regional deployments such as Advantage I-75, HELP/Cresent, Prepass and CVISN are making great strides towards improving the productivity of both enforcement officers and motor carriers at weigh stations. One of the significant technical advances that have helped lead to these improvements is the development of weigh-in-motion systems. In conjunction with other technologies, weigh-in-motion systems are used to screen out overweight commercial vehicles approaching the weigh stations. Unfortunately, a large majority of carriers are not participating in the programs such as Advantage I-75 and are still required to stop at the weigh-stations. Furthermore, although existing commercially available WIM systems can be use as screening devices they do not provide the accuracy required ( less than 1%) for final certification and ticketing of overweight vehicles. There is considerable room for improvement in accuracy and variability in the commercial WIM systems.
At best, weight enforcement activities are slow and cumbersome causing substantial overcrowding at weigh stations. Law enforcement officials are forced to either create unsafe conditions by allowing vehicles to backup in long lines near the weigh station entrance ramps or allow carriers to bypass weigh stations completely. Each day several thousand carriers travel by various weigh stations. Approximately 70% of these vehicles bypass the weigh stations due to the overcrowded conditions. Traffic simulations of a low-speed WIM system indicate one can reduce the average delay for a motor carrier from 280 seconds to 40 seconds and eliminate vehicles bypassing the weigh station. The successful implementation of converting a static scale to a high-accuracy, low-speed weigh-in-motion system will allow weight enforcement officials to weigh all carriers thus increasing productivity and operational efficiency through increased throughput.
Conventional WIM systems used today are plagued with problems of accuracy. Mainline WIM systems have a typical accuracy error of greater than 5%. This fact limits their utility in enforcement and other applications because users often do not trust the measurements obtained.
Although the above prior art may include advantages, improvements in the art are always needed. Therefore it is an object of the present invention to provide a weigh-in-motion (WIM) method and apparatus which is more accurate than the prior art.
The present invention overcomes deficiencies in the art by providing an apparatus and method which has improved accuracy. The apparatus is uniquely adaptable for converting in-ground static weighing scales for vehicles to weigh-in-motion systems, while still allowing the static scales to be used in static determinations if required. The apparatus upon conversion includes the existing in-ground static scale, tire presence switches and an electronic module. The apparatus allows for determination of when an axle of a vehicle is on the scale(s) at a given time, monitors the combined weight output from any given axle or axle combination on the scale(s) at any given time, and from these measurements automatically computes the weight of each individual axle, gross vehicle weight, and other desirable values by an integration and or signal averaging technique.
Therefore it is an object of the present invention to provide a method and apparatus for accurately weighing vehicles.
It is a further object of the present invention to provide a method and apparatus for accurately weighing moving vehicles.
It is a further object of the present invention to provide a method and apparatus for reliably weighing moving vehicles.
It is a further object of the present invention to provide a method and apparatus for quickly weighing moving vehicles.
It is a further object of the present invention to provide a method and apparatus for safely weighing moving vehicles.
It is a further object of the present invention to provide a method and apparatus for accurately weighing moving vehicles which is readily adaptable to existing static weighing systems.
Other objects, features, and advantages of the present invention will become apparent upon reading the following detailed description of the preferred embodiment of the invention when taken in conjunction with the drawing and the appended claims.